JP2559181B2 - Structure of receiving frequency converter in microwave detector - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave detector for detecting and notifying a microwave emitted from a measuring instrument or the like, and more particularly to a reception frequency for mixing a frequency of a radio wave received by a horn antenna and an output of a local oscillator. Related to the structure of the conversion unit.

[0002]

2. Description of the Related Art There has been known a microwave detector configured to detect a microwave emitted from a radar type speed measuring device and generate an alarm. In the case of general traffic monitoring radar type speed measuring equipment, 10G
Hz band (X band), 24 GHz band (K band), 35
A microwave in any band of the GHz band (Ka band) is used. A microwave detector having a speed measuring instrument of this type as a detection target device receives a microwave of a predetermined band by a superheterodyne circuit having the following configuration.

A horn antenna is generally used as a receiving antenna. A mixer diode is installed at the feeding point of the throat part of the horn antenna. In addition, a microwave circuit forming a local oscillator is provided at the back of the throat portion of the horn antenna. The frequency of the signal received by the horn antenna and the output of the local oscillator are mixed by the mixer diode. Further, an appropriate filter is provided between the mixer stage and the local oscillator so that the reception input by the horn antenna does not adversely affect the operation of the local oscillator. A type in which a mixer and a local oscillator are configured by a three-dimensional circuit using a waveguide and a type in which a mixer portion and a local oscillator are configured by a microwave integrated circuit using a microstrip line are known.

For example, the aforementioned X band, K band, Ka
If an attempt is made to construct a multi-band microwave detector that covers all the bands, one local oscillator cannot cover the entire reception band, and two different frequencies are used.
It is necessary to provide two local oscillators. The two local oscillators are selectively operated in a time division manner to switch the reception band. By doing so, one horn antenna and one mixer can realize multiband. A microwave detector having such a structure is disclosed in US Pat. No. 4,595,29.
No. 36.

[0005]

The above-mentioned US Pat. No. 49
In the prior art of 52936, the mixer circuit and the two local oscillators are formed by a microwave integrated circuit.
A microwave integrated circuit using a microstrip line is certainly excellent in terms of downsizing and no adjustment, but it is necessary to make the pattern accuracy of the strip conductor on the dielectric substrate fine, and advanced design technology is required. Not only is it required, but it is rather disadvantageous in terms of machining accuracy and part yield.

In the point, in the case of a three-dimensional circuit using a waveguide,
The characteristics can be easily adjusted by matching means such as iris and pins after the manufacture of the three-dimensional circuit body, and the know-how from such an adjustment technology has been accumulated for a long time. Therefore, the three-dimensional circuit is more advantageous in terms of ease of manufacture. However, conventionally, there has not been a multi-band microwave detector including one horn antenna, one mixer, and two local oscillators.

The present invention has been made in view of the above-mentioned conventional problems, and its object is to provide one horn antenna and one horn antenna.
It is to realize a multi-band microwave detector by a three-dimensional circuit in which two local oscillators are selectively combined with one mixer in a time division manner.

[0008]

The structure of the receiving frequency converting section in the microwave detector according to the present invention comprises a horn antenna, a two-port cavity in which one port is connected to the throat section of the horn antenna, and a two-port cavity. It has a three-dimensional circuit integrally formed with a one-port cavity in which one port is connected to the other port of the port cavity, and penetrates the inside and the outside of the main body of the three-dimensional circuit at an appropriate position.
In this state, a screw adjusting pin matching device is attached , a mixer diode is installed in the throat portion of the horn antenna, a first local oscillator is installed in the 2-port cavity, and a second local oscillator is installed in the 1-port cavity. It has a local oscillator installed.

[0009]

In the above structure, when the first local oscillator in the two-port cavity operates, the one-port cavity connected to the one-port cavity serves as an impedance section that is non-reflectively terminated. It is possible to realize good characteristics. Further, when the second local oscillator in the 1-port cavity operates, the 2-port cavity simply acts as a resonance element of the filter, so that good characteristics can be realized by simple adjustment using a pin matching device or the like.

[0010]

1 to 3 show the structure of a receiving frequency converter in a microwave detector according to an embodiment of the present invention. The three-dimensional circuit body 1 is composed of a base 1a and a cover 1b, which are made of aluminum die-cast with a substantially symmetrical shape. The base 1a and the cover 1b are assembled face-to-face with a parting line 1c, and both are fastened with seven screws 2. Thus, a microwave three-dimensional circuit including the elements described below is constructed.

The three-dimensional circuit body 1 has a horn antenna 3, a 2-port cavity 5 and a 1-port cavity 6.
It is 2 that follows immediately behind the throat part 4 of the horn antenna 3.
Port cavity 5, 1 port cavity 6 is 2
It is arranged beside the port cavity 5. Both the 2-port cavity 5 and the 1-port cavity 6 are square cavities.

One port 5a of the rectangular two-port cavity is directly connected to the throat portion 4 of the horn antenna 3, and the other port 5b is directly connected to the port 6a of the adjacent one-port cavity 6.

A mixer diode 7 is attached to the feeding point of the throat section 4 of the horn antenna 3. Also, 2
A series of printed wiring boards 8 are mounted in the port cavity 5 and the 1-port cavity 6. The printed wiring board 8 in the 2-port cavity 5 is mounted with the FET 9a and the dielectric resonance element 9b, which form the first local oscillator. Similarly, on the printed wiring board 8 in the 1-port cavity 6, an F which constitutes a second local oscillator is formed.
The ET 10a, the dielectric resonant element 10b, and the like are mounted.

Further, the three-dimensional circuit body 1 has a screw adjusting type 6
Book pin matchers 11a to 11f are attached. The pin matching device 11a is the dielectric resonance element 9 of the first local oscillator.
It is mounted right above b. The pin matching unit 11b is the second
Is mounted directly above the dielectric resonator element 10b of the local oscillator. The pin matching unit 11c is mounted on the connection passage of the port 5b of the 2-port cavity 5 and the port 6a of the 1-port cavity 6. The pin matching device 11d is mounted on the center of the throat portion 4 of the horn antenna 3. The pin matchers 11e and 11f are attached to the left and right positions before the throat portion 4 of the horn antenna 3.

The first local oscillators 9a and 9b in the two-port cavity 5 and the second local oscillators 10a and 10b in the one-port cavity 6 operate alternately in a time division manner. When the first local oscillators 9a and 9b in the 2-port cavity 5 operate, the local oscillation output is the 2-port cavity 5
Is output from the port 5a to the throat section 4 of the horn antenna 3, and is mixed in frequency with the antenna input by the mixer diode 7. During this operation, 1-port cavity 6
Acts as a non-reflective termination impedance.

When the second local oscillators 10a and 10b in the 1-port cavity 6 operate, the local oscillation output passes through the ports 6a, 5b, the 2-port cavity 5 and the port 5a, and the throat portion of the horn antenna 3 passes through. 4 and the frequency is mixed with the antenna input by the mass diode 7. In this operation, the 2-port cavity 5 acts as a resonance element of the filter.

Therefore , the inside and outside of the three-dimensional circuit main body 1 are appropriately positioned.
The six screw-adjustable pins mounted in a penetrating state
By adjusting the matching units 11a to 11f, it is possible to easily optimize the characteristics when the first local oscillator is operating and when the second local oscillator is operating.

[0018]

As described in detail above, according to the present invention, a three-dimensional circuit having a structure in which a two-port cavity and a one-port cavity are connected in series is provided in the throat of the horn antenna, and the main body of the three- dimensional circuit is provided. Inside and outside at appropriate positions
Install the screw-adjustable pin matcher while
The mixer diode is installed in the antenna throat part in
Since the first and second local oscillators are provided in the port cavity and the one-port cavity, respectively, when operating the first local oscillator and the second local oscillator alternately in a time-sharing manner, the key points of the three-dimensional circuit are required. It is possible to easily optimize the characteristics of each of the two local oscillators at the time of operation with a simple adjusting means such as a screw adjusting type pin matching device provided in. Therefore, a multi-band microwave detector in which two local oscillators are combined for one horn antenna and one mixer is designed without depending on the microwave integrated circuit that requires advanced design technology and production technology. It can be realized at low cost with a three-dimensional circuit that is easy to produce and adjust.

[Brief description of drawings]

FIG. 1 is a plan view of a reception frequency conversion unit in a microwave detector according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA in FIG.

FIG. 3 is a sectional view taken along line BB in FIG.

[Explanation of symbols]

 1 3D Circuit Main Body 1a Base 1b Cover 1c Parting Line 3 Horn Antenna 4 Throat 5 5 Port Cavity 5a Port 5b Port 6 1 Port Cavity 6a Port 7 Mixer Diode 8 Printed Wiring Board 9a FET 9b Dielectric Resonant Element 10a FET 10b Dielectric Body Resonant Element 11a-11f Pin Matching Device

Claims (1)

(57) [Claims] 1. A horn antenna, a two-port cavity in which one port is connected to a throat portion of the horn antenna, and one port in the other port of the two-port cavity.
One of the ports has a three-dimensional circuit in which the one-port cavity connected are integrally formed, application of the body of the three-dimensional circuit
Pin adjuster with screw adjustment type that penetrates inside and outside at a convenient position
A mixer diode is installed in the throat portion of the horn antenna, a first local oscillator is installed in the 2-port cavity, and a second local oscillator is installed in the 1-port cavity. Structure of the reception frequency converter in the characteristic microwave detector.